App Dev Ado

8/8/2019 App Dev Ado

1/40

Introduction toADO.NET

Understanding ADO.NETCopyright by Application Developers Training Company and AppDev Products Company, LLC

All rights reserved. Reproduction is strictly prohibited.

Understanding ADO.NET

Introduction to ADO.NET

Sample Chapter*

*To obtain a complete copy of this course, visit www.appdev.com or call 800-578-2062.


2/40


Understanding ADO.NETCopyright by Application Developers Training Company and AppDev Products Company, LLC


Welcomeand thank you for choosing Application Developers Training Company (AppDev) toguide you through an in-depth exploration of the powerful features ofMicrosoft ADO.NET.

At AppDev, we are committed to delivering quality training to programmers and developers.AppDev is a member of the Microsoft Certified Solution Provider network and we provide service

and training for Microsoft product users. We have trained over 50,000 developers since we begantraining in 1993, proving that AppDev students learn what they need to become efficient andeffective developers.

The key to a successful learning experience is comprehensive courseware that you can easilyunderstand and apply to your work environment quickly. We are sure you will find our coursewareinvaluable as a guide throughout this seminar and as a reference tool in your future projects.

Founded by application developers for application developers, AppDev offers you the mosteffective and comprehensive training in North America for Microsoft .NET, Access, Active ServerPages, Visual Basic, VBA, Visual FoxPro, Visual InterDev, SQL Server, Developing Applicationswith Access and SQL Server, and XML. Our instructors are practicing developers who are

recognized experts, successful authors, sought after speakers, and experienced trainers ofapplication development techniques. They put their development experience to work with our

proven courseware to help you build your skills for the future. We are pleased to offer you this

opportunity to take advantage of their expertise to help you masterADO.NET.

AppDev holds seminars throughout the United States and our multiple course offerings, locations,

and dates provide you with many ways to fit AppDev training into your busy schedule. If you cantfind a time or date that works for your company or department, we can bring customized training to

you. For groups of six or more, we will send one of our qualified instructors to your location toteach courseware specifically tailored to your organizations needs.

We hope you find todays course beneficial in your effort to enhance your ADO.NET development

skills. Keep us in mind should you decide to further your education with this excellentdevelopment product. If you have any questions or comments about this course or other trainingthat we offer, please dont hesitate to call us at 1-800-578-2062. You can also visit our Web site athttp://www.appdev.comwhere you can view course schedules, outlines and descriptions, or even

look over some sample courseware.

7610 Executive Drive Eden Prairie, MN 55344

PH (800) 578-2062 (952) 943-1363 FAX: (952) 942-8452 www.appdev.com


3/40


Understanding ADO.NET 1-1Copyright by Application Developers Training Company and AppDev Products Company, LLC


Introduction to

ADO.NET

Objectives

Use the Wizards in Visual Studio .NET to create ADO.NET code and

bound forms.

Investigate the ADO.NET object model.

Learn about .NET data providers.

The files associated with this chapter are located in the following folders:

{My Documents}\ADONET\Intro

{My Documents}\ADONETLabs\IntroLab

{My Documents}\ADONETLabs\IntroLabCompleted


4/40


1-2 Understanding ADO.NETCopyright by Application Developers Training Company and AppDev Products Company, LLC


ADO.NET Code Created by VisualStudio

One of the advantages of using Visual Studio .NET to create data-bound

applications is that the development environment provides components and

wizards to automate the creation of data objects. The Data Form Wizard

creates a complete data-bound form that is fully functional, fetching data from

a database, creating navigation buttons, allowing you to perform inserts, edits

and deletions, and saving changes back to the database. The form isnt

perfectbut it can save you a lot of time.

The Data Form Wizard

The following demonstration walks you through the steps of using the Data

Form Wizard to create a Windows form that displays and allows you to edit

data from the Northwind Orders and Order Details tables. The completed

example in the Intro.sln solution is named frmWizardyou may want to

create your own example using another name for the finished form.

Try It Out!

Follow these steps to run the Data Form Wizard:

1. Right-clickon the project in the Solution Explorer window andchoose Add|Add New Item from the menu.

See frmWizard inIntro.sln


5/40

ADO.NET Code Created by Visual Studio



2. Select Data Form Wizard, as shown in Figure 1. Name the form and

clickOpen. This launches the wizard.

Figure 1. The Data Form Wizard.


6/40




3. ClickNext to bypass the introductory screen. Select the Create a new

dataset named option and name it dsOrders, as shown in Figure 2. If

you are running the wizard in the Intro.sln project, name it dsOrders1

to avoid conflicts with the completed solution. ClickNext.

Figure 2. Naming the new DataSet.

4. Click the New Connection button. Set the Data Link properties to

connect to the Northwind database in SQL Server. You can type a dot

in the server name combo box to connect to the local instance of SQL

Server, as shown in Figure 3. An alternative is to type (local) instead.ClickOKin the dialog box, and clickNext in the wizard.


7/40




Figure 3. Creating a new connection to the SQL Server Northwind database.

5. Select the Orders and Order Details tables by moving them to the

right-hand pane shown in Figure 4, and clickNext.

Figure 4. Selecting the Orders and Order Details tables.


8/40




6. Since theres more than one table involved, you need to create a

relationship so that the order details can be displayed as child records

for each order. Figure 5 shows the wizard with a named relationship

relOrdersDetails. The Parent table is Orders, and the Child table is

Order Details. The primary/foreign key relationship is on the OrderID

column. This reflects the relationship between the two tables in the

Northwind database.

Figure 5. Configuring the relationship between Orders and Order Details.


9/40




7. Click the right-arrow button (>) to add the relation to the Relations

box on the right side of the dialog box. It should now look like Figure

6. ClickNext.

Figure 6. Creating the relOrdersDetails relationship.

8. You then need to specify which columns youd like displayed on the

form. If you dont want the finished form to appear to be too cluttered,

de-select some of the columns in the Orders table, as shown in Figure

7. The values in the Orders table will be displayed in TextBox controls

on the finished form, and the values in the Order Details table will be

displayed in a DataGrid control. ClickNext.

Figure 7. Selecting columns for display on the form.


10/40




9. The wizard provides several options for laying out the data on the

form. For this example, select the Single record in individual

controls option and add all of the options for additional controls, as

shown in Figure 8. Dont worrythe order details will still be

displayed in a DataGrid control, while the column values from each

order will be displayed in a TextBox control. ClickFinish.

Figure 8. Selecting controls for the form.


11/40




Figure 9 shows the finished form in the designer. It may not look like

much estheticallyit could use a helping hand with form layoutbut all

of the controls on the form are fully operational. Note that there are four

separate components in the tray at the bottom of the form designer. These

components are used to create the ADO.NET objects needed to retrieve

and cache the data.

Figure 9. The frmWizard form in Design view.


12/40




10. To test the form, set it as the startup form for the project. Figure 10

shows the completed frmWizard at runtime (after the controls have

been slightly re-arranged).

Figure 10. The form the wizard creates at runtime.

If you play with the form, youll find that all of the controls work. However,

its not too difficult to break the form and cause a runtime error by clicking the

buttons in the wrong order. In a real-world application, youd want to put in

some state management for the form and more robust error handling.

The Code Generated by the Data Form Wizard

One thing that sets data binding in .NET apart from data binding in earliertechnologies is that the Data Form Wizard simply writes codeit does not

create any ActiveX controls, or black box objects that you have no control

over. You can examine the code generated to create the components displayed

in the tray by expanding the Windows Form Designer generated code region

in the code window.

Figure 11 shows a partial view of the code in this normally hidden region. This

code executes when the form loads. Dont worry about the details for

nowyoull have a chance to explore the ADO objects used later on.

See frmWizard.vb


13/40




Figure 11. Code generated by the Data Form Wizard.

Not all of the wizard-generated code is contained in the hidden region. Figure

12 shows the section of code the wizard wrote that updates the database.

Figure 12. Wizard-generated code that updates the database.

All of the code generated by the Data Form Wizard is fully commented, and

examining it can help you learn more about how ADO.NET works. The

ADO.NET classes, methods, and properties used in this code will be covered

in detail in the remainder of this course.


14/40




The DataSet

In addition to creating the form, the wizard also creates an additional object,

dsOrders.xsd, which contains schema information about the data being used.

When you double-click it to open it in the designer, there are two views, one

graphical and one XML. Figure 13 shows the graphical view.

Figure 13. The schema for the DataSet in graphical view.

Click the XML tab at the bottom of the designer and you can see the XML

notation for the schema information, as shown in Figure 14.

Figure 14. Schema information created by the wizard.

In addition to the XML schema file, the code also creates a Visual Basic file

named dsOrders.vb. Together, these comprise what is called a typed DataSet.DataSets are used for caching data after it has been retrieved from a data

source, and typed DataSets contain extra information about the schema, or

See dsOrders.xsd


15/40




structure, of the data, allowing them to run more efficiently and to be easier to

work with in code.

The Data Adapter Configuration Wizard

If you look at frmWizard in the designer, youll note the two components in

the tray below the formOleDbDataAdapter1 and OleDbDataAdapter2.

OleDbDataAdapter1 is used to fetch the data for the Orders table, and

OleDbDataAdapter2 is used to fetch the data for the Order Details table. There

are three different ways to modify the settings for these data adapters: the

Properties window shown in Figure 15, the Data Adapter Configuration

Wizard, or code. The Properties window and the Data Adapter Configuration

Wizard are just easy ways to modify code. You can also launch the Data

Adapter Configuration Wizard from the Configure Data Adapter link at the

bottom of the Properties window.

Figure 15. Data Adapter properties.

See frmWizard


16/40




Try It Out!

You can also launch the Data Adapter Configuration Wizard by right-clicking

on the OleDbDataAdapter1 component in the tray and choosing Configure

Data Adapter from the menu. Follow these steps to complete the wizard:

1. When the wizard launches, click the Next button to bypass the

introductory screen.

2. You can then choose to use the existing connection or click the New

Connection button to create a new one, as shown in Figure 16. In this

case, the existing connection works just fine. ClickNext.

Figure 16. Selecting the database connection.

3. The following wizard dialog box, shown in Figure 17, allows you to

choose from the following options: Use SQL statements, Create newstored procedures, orUse existing stored procedures. The first

option, using SQL statements, is the default. If you choose the second

option, the wizard will create stored procedures in the SQL Server

database to select and modify the data, and use those instead of direct

SQL statements. The third option, Use existing stored procedures,would work only if you had already created stored procedures in the

SQL Server database. ClickNext.


17/40




Figure 17. Choosing query options.

4. The next dialog box, shown in Figure 18, displays the base query

selecting all of the columns in the Orders table. To modify the query,

click the Query Builder button.

Figure 18. The query used for selecting data.


18/40




5. The Query Builder shown in Figure 19 allows you to modify the

SELECT statement by clicking on the check boxes next to each

column. You can access other menu options by right-clicking in the

builder. The Run menu item displays the finished result set. ClickOK

when finished.

Figure 19. Modifying the query.


19/40




6. Click the Advanced Options button. This dialog box determines

whether data can be modified in the database by choosing the

Generate Insert, Update and Delete statements option, as shown in

Figure 20. The Use optimistic concurrency option means that the

code generated will check the database to see if another user has

modified the data since the data was fetched. ClickOKand then

Finish.

Figure 20. Determining what happens when data is modified.

If youve made any changes in the wizard, then the code in the form will be

automatically updated to reflect your changes.

TIP: The wizards create connection strings for you that use your machine name as

the Workstation ID setting, as shown in Figure 21. If you plan to distribute

the form to other users, this may cause the project to fail since the

Workstation ID will be different. Once youre ready to distribute the

application, you can delete the Workstation ID setting in your code with no ill

effects. It is not exposed in the wizard dialog boxes or in the Properties

window.

Figure 21. The Workstation ID is hardwired by the wizards.


20/40




The ADO.NET Object Model

In order to understand the code that is created for you by the wizards in Visual

Studio .NET, you have to understand the ADO.NET object model. It works

very differently from older object models such as DAO and ADO, so itshelpful to understand the problems with the older object models and the needs

that drove the development of ADO.NET.

The Evolution of ADO.NET

ODBC

Microsofts first technology for providing generic data access was ODBC

(Open Database Connectivity). ODBC has been very successful, but it isdifficult to program against because it relies on old-style function

callssimilar to the Windows API. So soon after ODBC was first developed,

Microsoft began work on object-based methods that would be easier for

programmers to use.

DAO

Microsofts first object-based API for data access was DAO, which was

developed solely in relation to the Jet database engine. You could use DAO

from within Microsoft Access, or from Visual Basic to access data stored in a

Jet database. DAO worked well in a single-tier application where both the Jet

database and the application were running on the client computer, even if the

data was stored remotely on a file server.

RDO and ODBCDirect

However, DAO didnt work as well with other data sources, such as SQL

Server, because it required an instance of the Jet database engine to

communicate with the database server using ODBC, which added substantial

overhead. So Microsoft added RDO for Visual Basic developers, and

ODBCDirect for Access developers needing to access ODBC data sources

more efficiently.

ADO

The last product in the chain was ADO, which was designed as an all-purpose

API capable of accessing data in databases, Active Directory and email stores,

among others. The OLE DB interfaces that underlay ADO were designed to

provide generic access to all types of data, not just relational data.


21/40




ADO was designed to handle the needs of client-server applications before

Web applications became common. Although ADO supports disconnected

recordsets, ADO recordsets dont travel well across the Internet, requiring

COM marshaling to transmit them among the tiers in an n-tier application. Not

only does this require specialized code, it also prevents data from being shared

with applications on non-Windows platforms. In short, ADO works best in a

Windows-only environment, and isnt well suited to the Internet.

ADO.NET

When Microsoft designed ADO.NET, they based it on an entirely new

programming model that is completely different from that of ADO. The name,

ADO.NET, may mislead you into thinking that ADO.NET is simply the next

version of ADO, but nothing could be further from the truth. Instead of being

based on COM and Windows, ADO.NET is based on the .NET Framework

and XML, and it is designed around working with disconnected data in an n-

tier environment. Figure 22 diagrams the evolution of ADO.NET over the

years.

Figure 22. The evolution of ADO.NET.

ADO.NET provides the following benefits:

Scalability

Interoperability

Ease of programming

Performance


22/40




Scalability

More concurrent users can be supported using the disconnected model

employed by ADO.NET. Data is retrieved from a data store read-only and the

connection is closed. If data needs to be written back to the data store, another

connection is opened, the data source is modified, and then the connection is

closed again. Also, working with stored procedures is much easier inADO.NET than it was in ADO, and stored procedures provide the most

scalable and secure way to access and modify server data.

Interoperability

ADO.NET uses XML under the covers for all data transport. This allows you

to request data and move it from one place to another without requiring

specific APIs, software, or connectivity. XML has no runtime/transport

requirements, and no special code is required to marshal data across the

Internet.

Ease of Programming

The central object for managing data in ADO.NET is the DataSet, which better

reflects the structure of the underlying data through its DataTable and

DataRelation objects, which will be discussed in detail in the next section.

Typed DataSets provide increased safety and convenience when programming,

and ADO.NET in general ensures that data access technology is uniform and

that all components share common types, design patterns, and naming

conventions.

ADO combined many different capabilities in one objectthe recordset. In

ADO.NET these capabilities have been factored out among several more

specialized objectsDataTables for caching data, DataReaders for retrievingread-only data, and DataAdapters for filling DataTables and sending changes

back to the database.

Performance

The elimination of COM when marshaling data results in significant

performance benefits. In addition, ADO.NET provides data-engine-specific

providers for SQL Server and more recently, Oracle. The SqlClient provider in

ADO.NET takes advantage of SQL Servers native Tabular Data Stream

(TDS) protocol, which provides performance benefits that go beyond the

capabilities of an all-purpose provider such as ADO. The interfaces are the

same for all data sources, but the implementation can be tailored to optimizeperformance for each one with more freedom than was available in OLE DB.


23/40




Connected and Disconnected Objects

The ADO.NET architecture makes it ideal for disconnected, n-tier

applications, where the central concept is working with a disconnected set of

data. Figure 23 shows a simplified diagram of the ADO.NET object model,

reflecting its division into two separate parts. On the left are the .NET DataProvider objects, which communicate with the database and which are

different for each data source. On the right are the disconnected objects used

for caching and managing datathese objects can work directly with XML,

they must go through a provider-specific DataAdapter to work with other data

sources.

Figure 23. The ADO.NET object model.

.NET Data Provider Objects

The objects shown in the box on the left side of the diagram in Figure 23 are

all directly related to connecting to databases and either fetching or modifying

data. These objects are always part of a specific .NET data provider, of which

two shipped with the .NET Framework:

System.Data.OleDb: Used for working with any OLE DB data

source. It also supports existing ADO unmanaged providers (versions2.6 and earlier).

System.Data.SqlClient: Designed to be used specifically with SQL

Server 7.0 or later.

Newer additions available for download from Microsoft include ODBC and

Oracle providers. In addition, providers are becoming available from third

parties for DB2, MySQL, Sybase, and all the other common data engines.


24/40




The DataAdapter

TheDataAdapterrepresents a set of data commands and a databaseconnection. It can fill a DataTable object or a set of DataTables in a DataSet

by using its Fill method, and it transfers changes performed on DataTables

back to the database by using its Update method. A DataAdapter has four

Command properties:

SelectCommand

DeleteCommand

InsertCommand

UpdateCommand

Each of these properties contains a Command object that the DataAdapter

object uses for selecting or modifying data. You use the Fillmethod to execute

the SelectCommandto populate a DataSet. You call the Update method to go

through the rows in a DataTable and use the appropriate commands to perform

deletions, inserts, or updates, based on the changes that have been made to the

data since it was retrieved or last updated.

The Connection object represents the connection to the database, allowing youto open and close connections, which are pooled automatically and can be

made part of transactions.

The Commandobject allows you to execute provider-specific commands forretrieving or modifying data, using parameters if necessary.

TheDataReaderobject is analogous to a forward-only, read-only, server-sideADO Recordset. It is designed to fetch records from the data source in a

stream as quickly as possible.

Each data provider contains its own specialized versions of these classes. In

reality there is no DataAdapter objectonly a SqlDataAdapter, anOleDbDataAdapter, etc. The same specialization and naming applies to the

Connection, Command, Parameter, and DataReader objects.


25/40




.NET Data Providers

In this course, youll be working primarily with the System.Data.OleDb

provider and the System.Data.SqlClient provider. Figure 24 shows the classes

contained in the OleDb and SqlClient providers as viewed in the Object

Browser in Visual Studio .NET.

Figure 24. System.Data.OleDb and System.Data.SqlClient classes.

Even though you ran the Data Form Wizard against data in a SQL Server

database, it still used the OleDb provider to create all of the code in the form.

The downside of using wizards and builders in general is that you sacrifice full

control and efficiency. Although its more work, it is more efficient to create

your ADO.NET objects by hand, which youll learn to do in subsequent

chapters in this course. In some cases, you can use the wizards to get you

started, and then modify the code that they generate.

The OleDb and SqlClient providers are the only ones that shipped with the

product when version 1 was released. Since then, however, Microsoft has

released providers for ODBC data sources and for Oracle. In addition, several

third-party vendors have also created specialized .NET providers for MySQL,Sybase, and other data engines. A provider that is specifically tailored for your

database engine will usually provide better performance than a generic

provider like the ones for OleDb or ODBC.


26/40




The Data-Caching Objects

The objects shown on the right side of the diagram in Figure 23 do not depend

in any way on the data sources you are working with. In fact, they know

nothing about the database and are never directly connected to it. You can

combine data from many different sources in a single DataSet. You use the

DataSet and the other object types that it contains as an in-memory cache, to

hold and manipulate data, or to bind data to controls.

ADataSetcontains one or moreDataTable objects, and one or more

DataRelation objects, which define relationships between the tables. You mustuse a DataAdapter to fill a DataTable in a DataSet, or to move the data it holds

back to a data source. However, there is one important exception to this

ruleDataSets can work directly with XML, which is shown directly

connected to the box on the right in Figure 23. You can load data and/or

schema directly from XML or save to XML without using a DataAdapter.

DataSet Navigation

In an ADO Recordset, you started at the beginning with the first row, and

iterated through the records one at a time. Only one row at a time could be the

current row. In a DataTable, there is no concept of the current row. It is

possible to reference rows by their ordinal position, or by a primary key or

index. Because DataSets can contain multiple related DataTables, it is also

possible to navigate master-detail relationships based on DataRelation objects.

When it is necessary to keep track of which row in a DataTable is currently

being edited in a bound Windows form, a separate CurrencyManagerobject isused.

DataTables and DataColumns

Each DataTable contains one or moreDataColumn objects. DataColumnscontain schema information, such as the data type, and whether null values are

allowed. DataColumns can have auto-incrementing functionality and can

contain expressions to automatically calculate values. In addition, you can

create event handlers that run when values in the column change.

DataRows

Each DataTable contains one or moreDataRow objects, which contain theactual data read from the data source. As with DataColumns, you can create

event handlers to respond to changes in DataRows.


27/40




Constraints

Each DataTable has a ConstraintCollection that can contain one or more

constraints. There are two kinds of constraint objectsUniqueContraints and

ForeignKeyConstraints.

You can implement a UniqueConstraintto ensure that the data in a column (orcombination of columns) is always unique. AForeignKeyConstraintensures

that values in a column are found in another tablefor example, that the

CustomerID values in an Order table correspond to values found in the

Customers table. ForeignKeyConstraints also determine what happens when

data in a parent table is changed. For example, a ForeignKeyConstraint could

be used to automatically delete all child rows if a parent row is deleted, or to

disallow deletion of the parent record as long as related child rows exist.

DataRelations

All the data contained in DataSets is held in DataTable objects. However,DataSets are much more than mere collections of DataTable objects. As you

can see in Figure 23, each DataSet also has aDataRelationCollection, whichcontains DataRelation objects. DataRelations are distinct from Constraints in

ADO.NET. You can have relations without constraints or constraints without

relations. DataRelations are used for navigating between parent and child rows

in related tables, and to define hierarchical nesting in XML.

DataViews

There is one additional important object type not shown in Figure 23the

DataView. DataViews allow you to customize multiple views of a DataTableobject. DataViews possess additional functionality not available in aDataTable that allows you to sort, filter, and find rows in DataTables.

DataViews also allow you to specify whether rows can be added, edited, or

deleted.

XSD Schema Files and Typed DataSets

XML is used whenever a DataSet is persisted to a file or a stream for transport.

The schema for a DataSetthe tables, columns, data types, constraints, and

relationshipsis represented as XML Schema (XSD), which can be in thesame document as the XML data or in a separate document. This allows the

structure of the data to be serialized for transport or saved to disk, and

recreated later.

XSD Schema documents can also be used to create special DataSets, called

typed DataSets. These are classes derived from the generic DataSet class, with

extra code added to create properties and methods that are specific to that

particular set of tables and columns. Typed DataSets make coding easier and

they improve runtime performance.The Data Form Wizard creates a typed


28/40




DataSet which you can view in the designer, as shown earlier in this chapter

with the dsOrders.xsd file.

Understanding the DataAdapter

Once you populate a DataSet with data from a database by calling theFillmethod of a DataAdapter or by loading data from an XML file, you can add,

edit, and delete records in the DataSet without affecting the database or XML.

This works because the DataSet is a private cache of data that is never

connected to the source of the data. As you add, edit, or delete rows in the

DataTables of a DataSet, both the original and current values are recorded, and

the RowState of each row keeps track of whether the row has been added,

edited, or deleted.

When you want to update a database based on changes in your DataSet, you

need a separate DataAdapter for each DataTable in the DataSet. When you call

the Update method of the DataAdapter, it executes the appropriate SQL

command or stored procedures for each row that has changed, based on theRowState.


29/40




Summary

The Data Form Wizard creates a fully-functional data-bound form.

The Data Form Wizard is a code generator, writing code to implementthe objects it creates.

A typed DataSets contains extra information about the schema, or

structure, of the data.

The DataAdapter Configuration Wizard lets you create or change a

DataAdapter object that communicates with the database.

Microsofts first object-based API for data access was DAO, which

was developed solely in relation to the Jet database engine.

RDO was added for Visual Basic developers, and ODBCDirect for

Access developers needing to access ODBC data sources.

ADO was designed as an all-purpose API capable of accessing data

stored in databases, spreadsheets, and text files, among others.

ADO.NET is based on an entirely new programming model that is

completely different from that of ADO.

ADO.NET provides scalability, interoperability, ease of programming,

and enhanced performance.

The ADO.NET architecture makes it ideal for disconnected, n-tier

applications.

System.Data.OleDb and System.Data.SqlClient are the two providers

that shipped with .NET.

The DataAdapter represents a set of data commands and a database

connection.

A DataSet contains one or more DataTable objects, and one or more

DataRelation objects, which define relationships between the tables.

Each DataTable has a ConstraintCollection that can contain one or

more constraints.

DataViews allow you to customize multiple views of a DataTable

object.

You can add, edit, and delete records in the DataSet without affecting

the database or XML.

You need a separate DataAdapter for each DataTable in the DataSet to

make changes to a database.

XML is used whenever a DataSet is persisted to a file or a stream for

transport.

XSD Schema documents are used to create typed DataSets.


30/40




(Review questions and answers on the following pages.)


31/40




Questions

1. True/False: The DataForm Wizard creates a form that does not allow you

to save changes back to a database.

2. What extra information does a typed DataSet contain?

3. Which are the two data providers that shipped with .NET?

4. Which ADO.NET object represents a set of data commands and a database

connection?

5. Which object would you use to create multiple views of a DataTable?

6. What is used when a DataSet is persisted to a file or a stream for transport?


32/40




Answers

1. True/False: The DataForm Wizard creates a form that does not allow you

to save changes back to a database.

FalseThe DataForm Wizard creates a fully-functional form.2. What extra information does a typed DataSet contain?

Information about the schema and structure of the data

3. Which are the two data providers that shipped with .NET?

System.Data.OleDb and System.Data.SqlClient

4. Which ADO.NET object represents a set of data commands and a database

connection?A DataAdapter

5. Which object would you use to create multiple views of a DataTable?A DataView

6. What is used when a DataSet is persisted to a file or a stream for transport?XML


33/40




Lab 1:


TIP: There is no completed sample for this lab.


34/40

Lab 1:




Lab 1 Overview

In this lab youll learn how to run the Data Form Wizard and how to use the

Data Adapter Configuration Wizard.

To complete this lab, youll need to work through two exercises:



Each exercise includes an Objective section that describes the purpose of the

exercise. You are encouraged to try to complete the exercise from the

information given in the Objective section. If you require more information to

complete the exercise, the Objective section is followed by detailed step-by-

step instructions.


35/40





ObjectiveIn this exercise, youll use the Data Form Wizard to create a form based on the

Categories and Products tables in the Northwind SQL Server database.

Things to Consider

How do you launch the Data Form Wizard?

Step-by-Step Instructions

1. Open the IntroLab.sln file.

2. Right-clickon the IntroLab project in the Solution Explorer window

and choose Add|Add New Item from the menu.

3. Select Data Form Wizard. Name the form frmProducts.vb and click

Open to launch the wizard.

4. ClickNext to bypass the introductory screen. Select the Create a new

dataset named option and name it dsProducts. ClickNext.


36/40

Lab 1:




5. If you do not have an existing connection to the Northwind SQL

Server database, clickNew Connection. Fill in the Data Link

properties as shown in Figure 25. ClickOKand then Next.

Figure 25. Fill in the Data Link Properties dialog box to connect to your localcopy of the Northwind database.

6. Select the Categories and Products tables by moving them to the

right-hand pane. ClickNext.

7. Create a relationship and name it relCatProducts. Select Categoriesfrom the Parent table drop-down list, and select Products from the

Child table drop-down list. Select CategoryId in the second drop-

down list under both Parent table and Child table. This is the

primary/foreign key relationship between Categories and Products.

This reflects the relationship between the two tables in the Northwinddatabase. Click the wedgie button (>) to add the relation to the

Relations box on the right side of the dialog box. This removes all of

your selections in the drop-down list boxes and you will see only the

relCatProducts name in the Relations pane. ClickNext.


37/40




8. Clear the Description check box as shown in Figure 26 and click

Next.

Figure 26. Clearing the Description check box will cause the Description to not

show up on the final form.

9. Select the Single record in individual controls option and leave all of

the other check boxes checked. ClickFinish.

10. Note that two items have been added to the Solution Explorer, as

shown in Figure 27.

Figure 27. The dsProducts.xsd and the frmProducts.vb files have been added to

the project by the Data Form Wizard.

11. Right-click on the IntroLab project and choose Properties. Select

frmProducts from the Startup object drop-down list. ClickOK.

12. Press F5 to run the project. Test the form and make sure that its

working properly.


38/40

Lab 1:




13. If you have time, take a look and explore the code that the wizard

generated.


39/40




The Data Adapter ConfigurationWizard

Objective

In this exercise, youll run the Data Adapter Configuration Wizard to revise

the original query that selected all of the records from the Products table so

that it does not display discontinued products.

Things to Consider

How do you launch the Data Adapter Configuration Wizard?

How do you revise the existing query?

Step-by-Step Instructions

1. Open frmProducts in the designer if it is not already open. You will

notice that there are two OleDbDataAdapter objects in the well.

2. Right-clickon OleDbDataAdapter2 and choose Configure Data

Adapter from the menu. When the wizard launches, click the Next

button to bypass the introductory screen.

3. In the Choose Your Data Connection dialog box, select the

connection you used in Exercise 1 from the drop-down list box and

clickNext.

4. In the Choose a Query Type dialog box, choose Use SQL statements

and clickNext.


40/40

Lab 1:


5. In the Generate the SQL Statements dialog box, click the Query

Builder button. In the Criteria column, type the expression =0. Clear

the check box in the Products column list. The Query Builder window

should look like Figure 28. ClickOK.

Figure 28. Setting a criteria to only display products that have not been

discontinued.

6. ClickNext and then Finish.

7. To test your changes, press F5 to run the project. Discontinuedproducts will no longer be displayed.